College

Two hockey players are about to collide on the ice. One player has a mass of 65 kg and is traveling at [tex]$1.8 \, \text{m/s}$[/tex] east. The other has a mass of 70 kg and is traveling at [tex]$1.4 \, \text{m/s}$[/tex] west. The system consists of the two hockey players.

According to the law of conservation of momentum, what is the total momentum of the system after they collide? Assume the collision is an elastic collision.

A. [tex]$19 \, \text{kg} \cdot \text{m/s}$[/tex] east
B. [tex]$215 \, \text{kg} \cdot \text{m/s}$[/tex] west
C. [tex]$19 \, \text{kg} \cdot \text{m/s}$[/tex] west
D. [tex]$215 \, \text{kg} \cdot \text{m/s}$[/tex] east

Answer :

To determine the total momentum of the system after the collision, we'll use the law of conservation of momentum. This principle states that the total momentum of a closed system remains constant if no external forces act on it.

Here's how we solve the problem:

1. Identify the mass and velocity of each hockey player:
- The first player has a mass of 65 kg and is traveling east at a speed of 1.8 m/s.
- The second player has a mass of 70 kg and is traveling west at a speed of 1.4 m/s.

2. Calculate the momentum of each player:
- Momentum is calculated by multiplying mass by velocity.

- For the first player (moving east):
[tex]\[
\text{Momentum}_1 = 65 \, \text{kg} \times 1.8 \, \text{m/s} = 117 \, \text{kg} \cdot \text{m/s}
\][/tex]

- For the second player (moving west, which we'll consider as negative direction):
[tex]\[
\text{Momentum}_2 = 70 \, \text{kg} \times (-1.4) \, \text{m/s} = -98 \, \text{kg} \cdot \text{m/s}
\][/tex]

3. Add the momenta to find the total momentum of the system:
- The total momentum is the sum of the momenta of both players:
[tex]\[
\text{Total Momentum} = 117 \, \text{kg} \cdot \text{m/s} + (-98 \, \text{kg} \cdot \text{m/s}) = 19 \, \text{kg} \cdot \text{m/s}
\][/tex]

Since the resulting total momentum is positive, it indicates the direction of the total momentum is east.

Therefore, the total momentum of the system after the collision is [tex]\(19 \, \text{kg} \cdot \text{m/s}\)[/tex] east. The correct choice is:
A. [tex]\(19 \, \text{kg} \cdot \text{m/s}\)[/tex] east.